JP5266705B2 - Communications system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent cluster synchronization from being polarized, and to select a node that becomes a suitable synchronization reference. <P>SOLUTION: In a communication system where a plurality of nodes that operate with different clocks communicate according to a time trigger scheme, one selected synchronization node is used as a synchronization master node to transmit a synchronization frame that becomes a cluster synchronization reference, clusters are synchronized on the basis of the synchronizing frame, and a monitor node judges whether or not a correction amount of a present node for the synchronization frame from the synchronization master node is settled within a set threshold range. On the basis of a result of the judgement, a next synchronization master node is enabled to judge whether to implement a change of the synchronization master node. Thus, the cluster is prevented from being polarized and a suitable synchronization node can be selected as a synchronization master node. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a communication system, and more particularly, to a synchronization control technique for synchronizing a plurality of communication apparatuses that are communicably connected.

  In recent years, automobiles have needs such as ecology, space saving and safety, and fine control such as high speed transmission, real time and high reliability is required. In order to meet this demand, each module in the automobile is being electronically controlled, and a plurality of electronic control units (ECUs) are mounted. A plurality of electronic control devices constitutes a network, and control information is exchanged by communication between the devices.

  In communication between electronic control devices, a communication protocol (for example, CAN which is an in-vehicle LAN standard) currently in widespread use is considered to have a shortage of capability as demand increases. Therefore, the FlexRay protocol has attracted attention as a next-generation communication method for in-vehicle networks. The FlexRay protocol is a communication method aiming at high reliability, and is expected to be applied in a control system and a safety system.

  The FlexRay protocol employs a time trigger method (in other words, a time division multiplexing method (TDMA method)) as a communication method, and communication is possible by synchronizing each node. However, in a network that performs FlexRay protocol communication (hereinafter also referred to as “FlexRay network”), there is no reference clock shared by nodes on the network. That is, in the FlexRay network, the strict absolute time as a whole is not specified.

  In the FlexRay network, each node synchronizes the cluster (network system) by calculating the global time with each clock (clock of its own node) based on the reception time of the synchronization frame transmitted from the synchronization node. . Here, the global time is a time as a cluster.

  In Patent Document 1 below, in an SDH transmission network in which a plurality of nodes are connected, a clock master node and a slave node are not fixed, a priority order is set for each clock of each node, and the clock master node is There has been proposed a clock synchronization control system in which other slave nodes synchronize their clocks according to their priorities. Further, it is described that, when an external clock connected to the determined clock master node fails, the node having the next highest priority clock is switched as a new clock master node and the clock is synchronized with the clock master node. ing.

  Patent Document 2 below proposes a LAN control mechanism for preventing communication failure when a master node that supplies a master clock goes down. Specifically, each node includes an oscillator that supplies an independent clock, and either a clock generated in phase synchronization with the clock extracted by the receiving unit or a clock supplied from the oscillator is mastered by priority. It has been proposed to select as a clock.

JP 2003-51831 A Japanese Patent Laid-Open No. 6-291552

  In the FlexRay network, cluster synchronization first forms cluster synchronization with a leading startup node and a following startup node. Based on the synchronization parameters acquired at this time, the nodes in the current cluster and each node participating in the cluster synchronization perform corrections to form cluster synchronization. In this way, as shown in FIG. 14A, each node (node A101 to node H108 connected to the bus 109) in the cluster 110 establishes synchronization and performs communication in one global time.

  Since the cluster synchronization is formed as described above, the parameter serving as a reference for synchronization largely depends on the synchronization node at the start-up, and there is a possibility that the cluster synchronization is formed in a state greatly deviated from the center frequency. In the cluster synchronization, each node performs a correction using a fault-tolerant midpoint (FTM) algorithm and maintains a synchronization state based on a synchronization frame transmitted from each synchronization node.

  In this algorithm, when the load on the network is heavy, parameters used for correction calculation of end-to-end nodes are greatly different, and there is a possibility of causing cluster-synchronized polarization. That is, when the load on the network is heavy or the nodes forming the cluster are separated, synchronization is performed in two global times, and there is a risk of polarization within the cluster as shown in FIG. is there. In FIG. 14B, the nodes A101 to H108 connected to the bus 109 synchronize with the synchronization group A111 (node A101 to node D104) that established synchronization in the first global time, in the second global time. Shows a state of being polarized to the synchronization group B112 (node E105 to node H108).

  When such cluster-synchronized polarization occurs, the transmission / reception timing of the frame shifts, and the reception-side node cannot capture the frame. Therefore, the synchronization frame cannot be taken in, and the communication becomes impossible due to the out-of-synchronization state.

  An object of the present invention is to prevent the occurrence of polarization in cluster synchronization and to select a node serving as an appropriate synchronization reference.

A communication system according to the present invention is a communication device of a plurality of communication devices in a communication system, and monitors a first communication device that transmits a reference frame related to synchronization processing, and a first communication device. A second communication device that receives a reference frame sent from one communication device, sends information related to a correction amount with respect to the received reference frame as a decision result, and collects a decision result from the second communication device, And a third communication device that determines whether or not to change the communication device that transmits the reference frame based on the collected determination results. When it is determined that the third communication device changes the communication device that transmits the reference frame, one communication device is selected from the plurality of communication devices, and the communication device that transmits the reference frame is designated as the first communication device. Switch to the communication device selected from the communication devices .

  According to the present invention, one communication device among a plurality of communication devices is used as a reference, and synchronization processing of the communication devices is performed. Therefore, the occurrence of polarization is prevented, and the communication devices are polarized into a plurality of groups. Can be prevented. In addition, since the communication device that transmits the reference frame is appropriately changed according to the monitoring result of the communication device that transmits the reference frame by another communication device, the communication device that transmits the reference frame can be appropriately selected, and high quality Communication can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram illustrating a configuration example of a communication system according to an embodiment of the present invention.
In the communication system according to the present embodiment, a plurality of nodes (nodes A1 to H8) are connected via a bus 9 so as to communicate with each other. Each node operates with an independent different clock, and performs communication based on the FlexRay protocol. In FIG. 1, a communication system having eight nodes is shown as an example, but the present invention is not limited to this, and the number of nodes included in the communication system is arbitrary.

  The node A1, the node C3, the node E5, and the node H8 have functions as a synchronization node and a monitoring node. The node B2, the node D4, the node F6, and the node G7 have a function as a monitoring node.

  The synchronization node is a node capable of transmitting a synchronization frame, and is selected as a synchronization master node and a next synchronization master node according to priority. The synchronization master node is a synchronization node that transmits a synchronization frame serving as a reference for cluster synchronization. The next synchronization master node is a synchronization node having the next highest priority (having the right to become the next synchronization master node) after the synchronization master node.

  The monitoring node is a node that monitors the synchronization master node. The monitoring node determines whether the synchronization frame from the synchronization master node is within the correction threshold range of its own node and notifies the result. The determination result notified from the monitoring node is collected by the next synchronization master node, and it is determined whether or not to change the synchronization master node based on the result.

  As shown in FIG. 1, it is desirable that all nodes of the communication system in this embodiment have a function as a monitoring node. However, it does not necessarily have a function as a monitoring node, there may be a node that has only a function as a synchronization node, or there is a node that does not have any function as a synchronization node or a monitoring node. You may do it.

  FIG. 2 is a diagram illustrating an example of an applicable network topology in the present embodiment. Although a bus type communication system is illustrated in FIG. 1, the topology (cluster configuration) of the communication system in the present embodiment is not limited to the bus type as shown in FIG. A star type as shown in FIG. Further, a bus type and a star type mixed (hybrid type) as shown in FIG. 2C may be used.

FIG. 3 is a block diagram illustrating a configuration example of the synchronization node in the present embodiment.
The synchronization node 10 includes a CPU 11, a memory 12, and a communication controller 15, which are communicably connected via an internal bus.

  The CPU 11 comprehensively controls each component in the synchronization node 10. For example, the CPU 11 executes node initial setting processing, transmission / reception data control processing, and table management processing related to the synchronization node priority table 13 and the monitoring node table 14 stored in the memory 12. For example, the CPU 11 executes a master flag switching determination process or a next master flag switching determination process. The master flag and the next master flag will be described later.

  The memory 12 stores various processing programs and data for operating the synchronization node 10, and functions as a work area at the time of processing execution. The memory 12 stores a synchronization node priority table 13 and a monitoring node table 14. The synchronization node priority table 13 and the monitoring node table 14 are given as parameters common to the synchronization nodes at the stage of designing the communication system.

  The synchronization node priority table 13 is a table for managing the priority (priority) of the synchronization nodes in the cluster. For example, the slot numbers assigned to the nodes are associated with the priorities. The monitoring node table 14 is a table that defines a node that operates as a monitoring node in the cluster and monitors the synchronization master node. For example, the monitoring node table 14 stores a slot number allocated to the node that operates as the monitoring node. Yes. Thus, by providing the synchronization node priority table 13, the priority order of the synchronization nodes in the cluster can be arbitrarily set. Further, by providing the monitoring node table 14, it is possible to easily specify a node to be operated as a monitoring node in the cluster.

  Note that the synchronization node priority table 13 is provided when the priority order of the synchronization nodes is set in the order from the smallest or largest slot number assigned to the synchronization node, and the management of the priority order by the table is unnecessary. You don't have to. If all nodes in the cluster operate as monitoring nodes without selecting a node to operate as a monitoring node, the monitoring node table 14 may not be provided.

  The communication controller 15 includes a CPU interface unit 16, a message information unit 17, a schedule control unit 18, a cluster synchronization control unit 19, a register unit 22, and a bus transmission / reception control unit 24. The CPU interface unit 16 is an interface unit for communicating with the CPU 11 and the like via an internal bus.

  The message information unit 17 stores transmission / reception messages (transmission / reception data). Setting of transmission data to the message information unit 17 and reading of reception data from the message information unit 17 are performed by the CPU 11 via the CPU interface unit 16.

  The schedule control unit 18 manages and controls a communication schedule such as a slot configuration and a communication cycle, and controls the bus transmission / reception control unit 24. Furthermore, the schedule control unit 18 manages the master flag switching timing when the own node is a synchronous master node. In addition, when the own node is the next synchronization master node, the schedule control unit 18 manages the switching timing of the next master flag and the collection timing of the determination result notified from the monitoring node.

  The cluster synchronization control unit 19 includes a master control unit 20 and a next master control unit 21 and performs control related to cluster synchronization. The master control unit 20 notifies the CPU 11 via the CPU interface unit 16 when the own node is a synchronous master node and the next master flag is extracted from the frame received by the bus transmission / reception control unit 24. Upon receiving the notification, the CPU 11 performs a master flag switching determination process, and performs control to drop the master flag in a frame transmitted from the own node from the next communication cycle.

  The next master control unit 21 collects determination results at each monitoring node extracted from the frame received by the bus transmission / reception control unit 24 when the own node is the next synchronization master node. Further, the next master control unit 21 determines the synchronization master node obtained based on the collected determination result at the timing supplied from the schedule control unit 18 as inappropriate (NG), and the register unit 22. The determination result is compared with a determination value preset in the determination result NG node number register 23. As a result, the next master control unit 21 notifies the CPU 11 via the CPU interface unit 16 when the number of monitoring nodes that have determined that the synchronization master node is NG exceeds the determination value set in the register 23. In response to the notification, the CPU 11 switches the master flag and the next master flag, sets the next master flag of the frame transmitted from the own node in the next communication cycle, and sets the frame transmitted from the own node in the subsequent communication cycle. Control to drop the next master flag and set the master flag.

  The bus transmission / reception control unit 24 performs communication with other nodes via the BUS according to the timing (communication schedule) from the schedule control unit 18. Specifically, at the time of transmission, the bus transmission / reception control unit 24 reads transmission data from the message information unit 17 and transmits it to the BUS, and transmits control information related to cluster synchronization according to the state of the own node. In addition, the bus transmission / reception control unit 24 sets the reception data of the frame received via the BUS at the time of reception in the message information unit 17 and the cluster synchronization information extracted from the reception frame according to the state of the own node. Set in the synchronization controller 19.

FIG. 4 is a block diagram illustrating a configuration example of the monitoring node in the present embodiment.
The monitoring node 30 includes a CPU 31, a memory 32, and a communication controller 33, and these are communicably connected via an internal bus. The communication controller 33 includes a CPU interface unit 34, a message information unit 35, a schedule control unit 36, a cluster synchronization control unit 37, a register unit 39, and a bus transmission / reception control unit 41.

  The CPU 31 comprehensively controls each component in the monitoring node 30. For example, the CPU 31 executes a node initial setting process, a transmission / reception data control process, a management process for the synchronization determination threshold register 40 in the register unit 39, and the like. The memory 32 stores various processing programs and data for operating the monitoring node 30, and functions as a work area at the time of processing execution.

  The CPU interface unit 34 is an interface unit for communicating with the CPU 31 and the like via an internal bus. The message information unit 35 stores transmission / reception messages (transmission / reception data). Setting of transmission data to the message information unit 35 and reading of reception data from the message information unit 35 are performed by the CPU 31 via the CPU interface unit 34.

  The schedule control unit 36 manages and controls a communication schedule such as a slot configuration and a communication cycle, and controls the bus transmission / reception control unit 41. Furthermore, the schedule control unit 36 generates a correction value of the own node for the synchronization frame from the synchronization master node received by the bus transmission / reception control unit 41. That is, the schedule control unit 36 recognizes the difference between the global time based on the synchronization frame from the synchronization master node and the local time at the own node, and generates a correction value thereof.

  The cluster synchronization control unit 37 has a master determination control unit 38 and performs control related to cluster synchronization. The master determination control unit 38 compares the correction value for the synchronization frame generated by the schedule control unit 36 with the threshold set in the synchronization determination threshold register 40 in the register unit 39, and compares the comparison result with the bus transmission / reception control unit 41. Notify

  The bus transmission / reception control unit 41 communicates with other nodes via the BUS according to the timing (communication schedule) from the schedule control unit 36. The bus transmission / reception control unit 41 reads transmission data from the message information unit 35 and transmits it to the BUS at the time of transmission, and transmits a determination result (master determination flag) of the synchronous master node. The bus transmission / reception control unit 41 sets the reception data of the frame received via the BUS in the message information unit 35 at the time of reception.

FIG. 5 is a block diagram illustrating a configuration example of the synchronization / monitoring node in the present embodiment.
The synchronization / monitoring node 50 is a node having the functions of both the synchronization node and the monitoring node, and has the configuration of each of the synchronization node shown in FIG. 3 and the monitoring node shown in FIG.

  The synchronization / monitoring node 50 includes a CPU 51, a memory 52, and a communication controller 55, which are communicably connected via an internal bus. The communication controller 55 includes a CPU interface unit 56, a message information unit 57, a schedule control unit 58, a cluster synchronization control unit 59, a register unit 63, and a bus transmission / reception control unit 66.

  The CPU 51 comprehensively controls each component in the synchronization / monitoring node 50. For example, the CPU 51 executes node initial setting processing, transmission / reception data control processing, and table management processing. The table management process includes a management process related to the synchronization node priority table 53 and the monitoring node table 54 stored in the memory 52, and a management process for the registers 64 and 65 in the register unit 63. For example, the CPU 11 executes a master flag switching determination process or a next master flag switching determination process.

  The memory 52 stores various processing programs and data for operating the synchronization / monitoring node 50, and functions as a work area at the time of processing execution. The memory 52 stores a synchronization node priority table 53 and a monitoring node table 54. The synchronization node priority table 53 and the monitoring node table 54 are the same as the synchronization node priority table 13 and the monitoring node table 14 shown in FIG.

  The CPU interface unit 56 is an interface unit for communicating with the CPU 51 and the like via an internal bus. The message information unit 57 stores transmission / reception messages (transmission / reception data). Setting of transmission data to the message information unit 57 and reading of reception data from the message information unit 57 are performed by the CPU 51 via the CPU interface unit 56.

  The schedule control unit 58 manages and controls a communication schedule such as a slot configuration and a communication cycle, and controls the bus transmission / reception control unit 66. Further, the schedule control unit 58 manages the switching timing of the master flag when the own node is the synchronous master node, and from the switching timing and the monitoring node of the next master flag when the own node is the next synchronous master node. Manages the collection timing of notified judgment results. Further, when the own node is not the synchronization master node, the schedule control unit 58 generates a correction value of the own node for the synchronization frame from the synchronization master node received by the bus transmission / reception control unit 66.

The cluster synchronization control unit 59 includes a master control unit 60, a next master control unit 61, and a master determination control unit 62, and performs control related to cluster synchronization.
The master control unit 60 notifies the CPU 51 via the CPU interface unit 56 when the own node is a synchronous master node and the next master flag is extracted from the frame received by the bus transmission / reception control unit 66. In response to the notification, the CPU 51 performs a master flag switching determination process, and performs control to drop the master flag in a frame transmitted from the own node from the next communication cycle.

  When the own node is the next synchronization master node, the next master control unit 61 determines the determination result at each monitoring node extracted from the frame received by the bus transmission / reception control unit 66 (including the determination result at the own node). And the comparison between the number of monitoring nodes determined to be NG as the synchronization master node and the determination value set in the determination result NG node number register 64 is performed at a predetermined timing. As a result, the next master control unit 61 notifies the CPU 51 via the CPU interface unit 56 when the number of monitoring nodes that have determined that the synchronization master node is NG exceeds the determination value set in the register 64. In response to the notification, the CPU 51 performs a process of switching between the master flag and the next master flag, sets the next master flag of the frame transmitted from the own node in the next communication cycle, and sets the frame transmitted from the own node in the subsequent communication cycle. Control to drop the next master flag and set the master flag.

  The master determination control unit 62 compares the correction value for the synchronization frame generated by the schedule control unit 58 with the threshold set in the synchronization determination threshold register 65 when the node is not the synchronization master node, and determines the comparison result. Notify the bus transmission / reception control unit 66.

  The bus transmission / reception control unit 66 performs communication with other nodes via the BUS according to the timing (communication schedule) from the schedule control unit 58. At the time of transmission, the bus transmission / reception control unit 66 reads transmission data from the message information unit 57 and transmits it to the BUS, and transmits control information related to cluster synchronization according to the state of the own node. In addition, the bus transmission / reception control unit 66 sets the reception data of the frame received via the BUS at the time of reception in the message information unit 57, and the cluster synchronization information extracted from the reception frame according to the state of the own node. Set in the synchronization control unit 59.

FIG. 6 is a diagram illustrating an example of a frame format transmitted and received in the present embodiment.
In the present embodiment, the field NF is added to the conventional FlexRay frame format. In the frame format shown in FIG. 6, each field other than the field NF is the same as the conventional FlexRay frame format including a bit (Sync Frame Indicator) indicating whether or not it is a synchronization frame. Omitted (for example, see FlexRay Protocol Specification Version 2.1 Revision A).

  The field NF includes a master flag field, a next master flag field, and a master determination flag field. The “Reserved” bit in the field NF is provided to make the field NF a 1-byte field, and is not essential in the present embodiment.

  The master flag field is a 1-bit field assigned to a master flag indicating a synchronization node that is a reference for the current cluster synchronization. The synchronization master node sets a master flag in the master flag field and transmits a synchronization frame.

  The next master flag field is a 1-bit field assigned to the next master flag indicating the reference synchronization node for the next cluster synchronization. When the next synchronization master node is to be transferred, the next synchronization master node sets the next master flag in the next master flag field, sends a synchronization frame, and notifies the cluster.

  The master determination flag field is a 3-bit field assigned to the master determination flag indicating the determination result of the currently selected synchronous master node. Each monitoring node sets a bit pattern corresponding to the determination result of the synchronous master node in the master determination flag field, transmits a frame, and notifies the determination result in the own node in the cluster.

FIG. 7 is a diagram for explaining the master determination flag.
As shown in FIG. 7A, the own node (monitoring node) sets the correction value of the own node for the synchronization frame in which the master flag is set, that is, the synchronization frame from the synchronization master node, in the synchronization determination threshold register. Whether the correction is in the positive direction or the correction in the negative direction. In accordance with the determination result, the monitoring node sets a master determination flag for a frame to be transmitted as shown in FIG.

  When the correction is in the negative direction and the correction amount is within the threshold range (region P2 shown in FIG. 7A), the monitoring node sets the master determination flag of the frame to be transmitted to “000”. When the correction is in the negative direction and the correction amount is larger than the threshold (region P1 shown in FIG. 7A), the monitoring node sets the master determination flag of the frame to be sent to “001”. Similarly, when the correction is in the positive direction and the correction amount is within the threshold range (region P3 shown in FIG. 7A), the monitoring node sets the master determination flag of the frame to be transmitted to “010”. Set. When the correction is in the positive direction and the correction amount is larger than the threshold (region P4 shown in FIG. 7A), the monitoring node sets the master determination flag of the frame to be transmitted to “011”. If the synchronization frame with the master flag cannot be received, the monitoring node assumes that the synchronization master node is in a lost state, and sets the master determination flag of the frame to be transmitted to “1XX” (X is Don't Care). Set.

  Note that the setting example of the master determination flag shown in FIG. 7 is an example, and the present invention is not limited to this. It is only necessary that the determination result of the synchronous master node can be uniquely recognized by the bit pattern of the master determination flag.

  FIG. 8 is a diagram illustrating an example of a synchronization node priority table included in the synchronization node according to the present embodiment. The synchronization node priority table is a table for managing the priority (priority) of the synchronization nodes in the cluster, and the slot numbers assigned to the nodes are associated with the priorities. In the example shown in FIG. 8, the priority of the synchronization node to which the slot number (Slot 1) is allocated is high, and the slot number of the allocated synchronization node is the slot number (Slot 5), the slot number (Slot 3), and the slot number (Slot 8). ), ... in order of priority.

  For example, when the synchronization node to which the slot number (Slot 1) is allocated is the synchronization master node, the synchronization node to which the slot number (Slot 5) is allocated becomes the next synchronization master node. When the synchronization master node is shifted in this state, the synchronization node to which the slot number (Slot 5) is assigned becomes the synchronization master node, and the synchronization node to which the slot number (Slot 3) is assigned becomes the next synchronization master node. In addition, the priority of the synchronization node to which the slot number (Slot 1) is assigned becomes the lowest.

  FIG. 9 is a diagram illustrating an example of a monitoring node table included in the synchronization node according to the present embodiment. In the example shown in FIG. 9, in the cluster, nodes to which slot numbers (Slot1, Slot2, Slot3, Slot5, Slot6, Slot8) are assigned are defined as monitoring nodes. In this case, the next synchronization master node collects the determination results from each node to which the slot number (Slot1, Slot2, Slot3, Slot5, Slot6, Slot8) is allocated, and performs the migration of the synchronization master node. Judge whether or not.

Next, the synchronous master node transition operation in the communication system in the present embodiment will be described.
In the following description, the communication system according to the present embodiment includes the eight nodes (node A1 to node A8) illustrated in FIG. 1, and each node i (i = 1 to 8) is assigned a slot number (Sloti). Are allocated. The node A1, the node C3, the node E5, and the node H8 that are the synchronization nodes have the synchronization node priority table shown in FIG. 8 and the monitoring node table shown in FIG. That is, the priority order of the synchronization nodes is set in the order of node A1, node E5, node C3, and node H8, and node A1, node B2, node C3, node E5, node F6, and node H8 operate as monitoring nodes. Further, in the determination result NG node number register of each synchronization node, when the number of monitoring nodes determined to be NG as the synchronization master node is 4 or more, the synchronization master node is transferred. It is assumed that a determination value is set so as not to perform the transition.

As shown in FIG. 10, a case where the synchronization master node moves from the node A1 to the node E5 will be described as an example.
As shown in FIG. 11A, when the synchronization node (synchronization master node) selected on the basis of cluster synchronization is the node A1, the node A1 sets a master flag and transmits a synchronization frame. Each node in the cluster executes synchronization processing based on the synchronization frame sent from the node A1.

  In addition, each monitoring node (node B2, node C3, node E5, node F6, node H8) has its own node correction value for the synchronization frame in which the master flag is set, that is, the synchronization frame from node A1, within the threshold range. It is determined whether or not it exists, the determination result is set as a master determination flag, and a frame is transmitted to notify the cluster. Here, as shown in FIG. 12, the correction amount at the node B2 is within the negative threshold range, and the correction amounts at the other nodes (node C3, node E5, node F6, and node H8) are negative threshold values. Suppose that it is out of range.

  The node E5, which is a reference synchronization node (next synchronization master node) of the next cluster synchronization to be transferred, determines the master from the frame transmitted from each monitoring node (node B2, node C3, node E5, node F6, node H8). By extracting the flags, the judgment results at each monitoring node are collected. Further, the node E5, which is the next synchronization master node, determines the number of monitoring nodes determined that the node A1 is NG as the synchronization master node based on the collected determination results, and the determination value set in the determination result NG node number register. To determine whether or not to change the synchronization master node.

  In this example, since the four nodes (node C3, node E5, node F6, and node H8) have determined that the node A1 is the synchronization master node and are NG, the next synchronization master node, the node E5, It is determined that A1 is not appropriate as a synchronization master node. Then, in the next communication cycle (synchronization master transition cycle), as shown in FIG. 11B, the next synchronization master node E5 sets the next master flag and sends a synchronization frame to transition the synchronization master node. Is notified in the cluster. That is, when it is determined that the synchronization master node needs to be changed, the next synchronization master node sets the next master flag and sends a synchronization frame to notify the cluster.

  Note that in this synchronization master transition cycle, the node A1, which is the synchronization master node, sets the master flag and transmits the synchronization frame, but recognizes the synchronization frame on which the next master flag transmitted from another synchronization node is set. As a result, the master flag is cleared from the next communication cycle.

  As shown in FIG. 11C, the node E5 which was the next synchronization master node becomes a new synchronization master node in the next communication cycle following the synchronization master transition cycle, and the next master flag is cleared and the master flag is set. Send out a sync frame. Further, the node C3 having the second highest priority after the node E5 becomes the next synchronization master node. Each node in the cluster executes synchronization processing with reference to the synchronization frame sent from the node E5.

  In addition, each monitoring node (node A1, node B2, node C3, node F6, node H8) determines whether or not the correction value of the own node with respect to the synchronization frame from the node E5 where the master flag is set is within the threshold range. Is determined, the determination result is set as a master determination flag, and a frame is transmitted to notify the cluster. Here, as shown in FIG. 13, the correction amount at node A1 is outside the positive threshold range, the correction amounts at node B2, node C3, and node H8 are within the positive threshold range, and correction at node F6. Assume that the amount is within the negative threshold range. That is, among the five monitoring nodes, four monitoring nodes have a correction amount within the threshold range, and one monitoring node has a correction amount outside the threshold range.

  Node C3, which is the next synchronization master node, extracts the master determination flag from the frame transmitted from each monitoring node (node A1, node B2, node C3, node F6, node H8), and displays the determination result at each monitoring node. collect. Further, based on the collected determination results, the node E5 compares the number of monitoring nodes determined to be NG as a synchronization master node with the determination value set in the determination result NG node number register, and changes the synchronization master node. It is determined whether or not to implement.

  As described above, only one node A1 determines that the node E5 is NG with the synchronization master node as a node. Therefore, the node C3 which is the next synchronization master node determines that the node E5 is appropriate as the synchronization master node, and maintains the state without changing the synchronization master node.

  In the above description, the next synchronization master node determines the number of monitoring nodes for which the synchronization master node is determined to be NG based on the determination result at each monitoring node, and the determination value set in the determination result NG node number register. Based on the comparison result, it is determined whether or not to change the synchronization master node. However, there is a node in the cluster that is in the synchronization master node lost state based on the determination result at each monitoring node. In this case, the synchronization master node may be changed.

  According to this embodiment, one of a plurality of synchronization nodes is used as a synchronization master node, and a synchronization frame serving as a reference for cluster synchronization is transmitted from the synchronization master node, and cluster synchronization is performed based on this synchronization frame. Cluster polarization can be prevented from occurring, and nodes in the communication system can be prevented from being polarized into a plurality of groups.

  In addition, the node participating in the cluster synchronization determines whether or not the correction amount of the own node for the synchronization frame from the synchronization master node is within a set threshold range, and the number of nodes outside the threshold range is a predetermined number. If it exceeds, change the synchronization master node. As a result, an appropriate synchronization node can be selected as the synchronization master node serving as a cluster synchronization reference, and high-quality frame communication can be provided.

The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.
Various aspects of the present invention will be described below as supplementary notes.

(Supplementary note 1) A communication system in which a plurality of communication devices operating with independent different clocks communicate with each other in a time trigger method,
A first communication device that is one of the plurality of communication devices and transmits a reference frame for synchronization processing;
A determination result is collected from another communication device that is monitoring the first communication device, and a second determination is made as to whether or not to change the communication device that transmits the reference frame based on the collected determination result. A communication device,
If it is determined that the second communication device changes the communication device that transmits the reference frame, one communication device is selected from the plurality of communication devices and switched to the first communication device. A featured communication system.
(Supplementary Note 2) The communication device monitoring the first communication device has a difference between a time based on the reference frame transmitted from the first communication device and a time based on a clock in the communication device. The communication system according to appendix 1, wherein it is determined whether or not it is within a set threshold range and a determination result is transmitted.
(Appendix 3) Whether the communication device that is monitoring the first communication device is within a threshold range in which a correction value in the communication device for the reference frame transmitted from the first communication device is set The communication system according to appendix 1, wherein a determination result is determined and a determination result is transmitted.
(Supplementary note 4) When it is determined that the second communication device changes the communication device that transmits the reference frame, the second communication device is switched to the first communication device, and the plurality of communication devices The communication system according to supplementary note 1, wherein one communication device is selected from among the two as the second communication device.
(Additional remark 5) The said 2nd communication apparatus collects only the determination result which concerns on the said 1st communication apparatus from the designated communication apparatus in these communication apparatuses, The additional description 1 characterized by the above-mentioned. Communications system.
(Additional remark 6) The communication system of Additional remark 5 characterized by providing the table which defined the said designated communication apparatus from which the determination result which concerns on a said 1st communication apparatus is collected.
(Supplementary note 7) The second communication device compares the number of communication devices determined based on the determination result that the first communication device is not suitable as a reference for synchronization with the set number of communication devices, The communication system according to appendix 1, wherein it is determined whether or not to change a communication device that transmits the reference frame.
(Supplementary note 8) The communication system according to supplementary note 1, wherein the first communication device and the second communication device are selected from the plurality of communication devices in a predetermined order.
(Supplementary Note 9) A table defining priorities selected as the first communication device and the second communication device is provided, and the first communication device and the second communication device are selected from the plurality of communication devices according to the table. 9. The communication system according to appendix 8, wherein each of the two communication devices is selected.
(Supplementary note 10) The supplementary note 8, wherein the first communication device and the second communication device are respectively selected from the plurality of communication devices according to a transmission order of frames allocated to the communication devices. Communication system.
(Supplementary note 11) The communication system according to supplementary note 1, wherein a field indicating the determination result is provided in a frame transmitted and received between the communication devices.
(Supplementary note 12) The communication system according to supplementary note 1, wherein a field for setting a flag indicating the reference frame is provided in a frame transmitted and received between the communication devices.
(Supplementary note 13) The communication system according to supplementary note 1, wherein a field for setting a flag indicating that the communication device that transmits the reference frame is changed is provided in a frame transmitted and received between the communication devices. .

It is a figure which shows the structural example of the communication system in embodiment of this invention. It is a figure which shows the example of the network topology applicable in this embodiment. It is a figure which shows the structural example of the synchronous node in this embodiment. It is a figure which shows the structural example of the monitoring node in this embodiment. It is a figure which shows the structural example of the synchronization and monitoring node in this embodiment. It is a figure which shows an example of the frame format transmitted / received in this embodiment. It is a figure for demonstrating a master determination flag. It is a figure which shows an example of a synchronous node priority table. It is a figure which shows an example of the monitoring node table. It is a figure which shows the synchronous master node transfer operation | movement in this embodiment. It is a figure for demonstrating the state in each cycle of synchronous master node transfer operation. It is a figure which shows an example of the determination result of synchronous master determination. It is a figure which shows an example of the determination result of synchronous master determination. It is a figure for demonstrating the cluster synchronization in a FlexRay network.

Explanation of symbols

1 to 8 nodes 9 buses 10 synchronization nodes 30 monitoring nodes 50 synchronization / monitoring nodes 11, 31, 51 CPU
12, 32, 52 Memory 13, 53 Synchronization node priority table 14, 54 Monitoring node table 15, 33, 55 Communication controller 16, 34, 56 CPU interface unit 17, 35, 57 Message information unit 18, 36, 58 Schedule control Unit 19, 37, 59 Cluster synchronization control unit 20, 60 Master control unit 21, 61 Next master control unit 38, 62 Master determination control unit 22, 39, 63 Register unit 23, 64 Determination result NG node number register 40, 65 Synchronization Determination threshold register 24, 41, 66 Bus transmission / reception control unit

Claims (8)

A communication system in which a plurality of communication devices operating with independent different clocks communicate with each other in a time trigger method,
A first communication device that is one of the plurality of communication devices and transmits a reference frame for synchronization processing;
A second communication device that monitors the first communication device, receives the reference frame transmitted from the first communication device, and transmits information on a correction amount for the received reference frame as a determination result; ,
The second collects the determination result from the communication device, collected on the basis of the determination result and a third communication device that determines whether or not to change the communication device for sending said reference frame,
If the third communication device determines to change the communication device that transmits the reference frame, a communication device that selects one communication device from the plurality of communication devices and transmits the reference frame is selected. , a communication system, characterized in that switching from the first communication device to said selected communication device. The information related to the correction amount for the reference frame transmitted from the second communication device includes a time based on the reference frame transmitted from the first communication device, and a time based on a clock in the communication device. The communication system according to claim 1 , further comprising information indicating whether or not the difference is within a set threshold range. The information related to the correction amount for the reference frame transmitted from the second communication device is within a threshold range in which a correction value in the communication device for the reference frame transmitted from the first communication device is set. The communication system according to claim 1 , further comprising information indicating whether or not. When the third communication device determines to change the communication device that transmits the reference frame, the communication device that transmits the reference frame is switched from the first communication device to the third communication device , The communication device that selects one communication device from the plurality of communication devices and collects the determination result is switched from the third communication device to the selected communication device. The communication system according to any one of? The said 3rd communication apparatus collects only the determination result which concerns on the said 1st communication apparatus from the said 2nd communication apparatus designated in the said some communication apparatus. 5. The communication system according to any one of 4. The third communication device is a communication device having the second highest priority after the first communication device as a candidate of a communication device that transmits the reference frame among the plurality of communication devices. The communication system according to claim 1. A table defining priorities selected as the first communication device and the third communication device is provided, and the first communication device and the third communication device are selected from the plurality of communication devices according to the table. The communication system according to claim 1, wherein each is selected. 2. The communication system according to claim 1, wherein the first communication device and the third communication device are respectively selected from the plurality of communication devices in accordance with a transmission order of frames allocated to the communication devices. .

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